Multiple cylinder drier in a paper machine

ABSTRACT

An improvement in the multiple cylinder drier unit of a paper making machine, each drying group of which consists of a number of driers disposed in two rows, one above the other, and lapped by the paper web running through the group in zigzag fashion, supported by a drying wire. The suggested improvement is particularly characterized in that the driers in one row of the drying group are permeable to air and that the multiple cylinder drier also comprises additional driers for creating differential pressures on both sides of the paper web, whereby passage of air through the web is achieved, with the web pressed into contact with the drying wire. According to further, optional features of the invention, the drying means permeable to air are cylindrically shaped drying cylinders, or they consist of a suction chamber substantially confined by the drying wire moving on a support of guiding rolls. In addition, hot air blowing hoods may be arranged around the drying means permeable to air and, within them, suction chambers. The paper web arriving from the press section of the paper machine may be arranged to be attached to the drying wire by the aid of suction means exerting suction through this wire.

Kankaanpaa 1 Apr. 1,1975

[ MULTIPLE CYLINDER DRIER IN A PAPER [56] References Cited UNITED STATESPATENTS 1,615,210 1/1927 Astcn 34/116X 1,767,889 6/1930 .lurgensen162/290 X 1,844,658 2/1932 Holcomb 34/159 2,091,805 8/1937 Chuse 162/290X 3,318,017 5/1967 Smith, Jr 34/116 3,320,675 5/1967 Chaikin et al.34/115 X 3,576,078 4/1971 Holt 34/159 X 3,671,389 6/1972 Wahlstrom etal, 162/306 3,685,167 8/1972 Loveday et a1. 34/155 X 3,733,711 5/1973Haythornethwaite 34/155 X 3,816,941 6/1974 Hulik et a1, 162/207 XPrimary E.\'uminerRobert L. Lindsay, Jr. Assistant Examiner-Richard V.Fisher Attorney, Agent, or FirmRichards & Geier [57] ABSTRACT Animprovement in the multiple cylinder drier unit of a paper makingmachine, each drying group of which consists of a number of driersdisposed in two rows, one above the other, and lapped by the paper webrunning through the group in zigzag fashion, supported by a drying wire.The suggested improvement is particularly characterized in that thedriers in one row of the drying group are permeable to air and that themultiple cylinder drier also comprises additional driers for creatingdifferential pressures on both sides of the paper web, whereby passageof air through the web is achieved, with the web pressed into contactwith the drying wire.

According to further, optional features of the invention, the dryingmeans permeable to air are cylindrically shaped drying cylinders, orthey consist of a suction chamber substantially confined by the dryingwire moving on a support of guiding rolls. in addition, hot air blowinghoods may be arranged around the drying means permeable to air and,within them, suction chambers. The paper web arriving from the presssection of the paper machine may be arranged to be attached to thedrying wire by the aid of suction means exerting suction through thiswire.

MULTIPLE CYLINDER DRIER IN A PAPER MACHINE The present inventionconcerns, in a paper making machine, a multiple cylinder drier havingone or several drying groups or drying sections composed of drying meansdisposed in two rows, one above the other, over which the paper webtravels along a zigzag path from one row to the other, through the groupand is supported by a drying wire permeable to air. In multiple cylinderdriers of this kind, all drying means have previously been soconstructed that the drying has taken place according to the contactdrying method. As a result, the efficiency of the drier has not been ashigh as it could be. Since paper machines are nowadays run at high speedand the speed is increased all the time, the multiple cylinder drier isrequired to be more efficient in order that a desired degree of dryingof the paper web might be achieved. Consequently, the multiple cylinderdrier has to be very large indeed, which has its own drawbacks.

The object of the present invention is to provide a more efficientmultiple cylinder drier, in order that the above-mentioned drawbackcould be eliminated. The invention is characterized in that in amultiple cylinder drier of the kind described the drying means of onerow are permeable to air and that the multiple cylinder drier alsocomprises means for creating differential pressures on both sides of thepaper web, whereby the drying air can be made to pass through the paperweb, while this paper web is urged into contact with the drying wire.Since the multiple cylinder drier according to the invention hasalternating contact drying means and perfusion drying means, theadvantages of the contact drying method and of the perfusion dryingmethod can be combined. It follows that the drying efficiency of amultiple cylinder drier according to the invention is considerablysuperior to that of multiple cylinder driers of prior art.

The drying means permeable to air may be cylinders permeable to air suchas those provided with a cylinder mantle. The drying means permeable toair may also consist of suction chambers substantially confined by thedrying wire, moving on the support of guiding rolls. In order to createdifferential pressures, around the drying means permeable to air a hotair blowing hood may be arranged, and inside it a suction chamber.

The invention is more thoroughly described with reference to theembodiment examples presented in the attached drawings.

In the drawing,

FIG. 1 shows schematically a multiple cylinder drier according to anembodiment example of the invention, in elevational view.

FIG. 2 shows a multiple cylinder drier according to another embodimentexample of the invention, similarly in schematical presentation and inelevational view.

In the multiple cylinder drier of FIG. 1 the drying means have beendisposed, interspaced, in two rows one above the other. The drying meansin the lower row are conventional heatable drying cylinders 30, 3b. Eachdrying means in the upper row comprises suction rolls 4 and guidingrolls 6 disposed between these, and which constitute a curved path,along which the drying wire permeable to air travels. The drying wireconsists most appropriately of a plastic wire or equivalent, which doesnot take up water. Over the curved path a heavy-duty hot air drying hood7 has been fitted, and under it, within the curved part, a suctionchamber 8. In addition, there are means for conducting the paper web tothe multiple cylinder drier. These means consist of a suction roll 1,followed by a suction box 2.

The paper web 9 arriving from the press section of the paper machine isdrawn against the drying wire 5 by the use of the suction roll 1, andits attachment to this wire is aided by the suction box 2. Subsequently,the paper web 9 travels, impacted between the drying cylinder 30 and thedrying wire 5, up to the press nip 3a/4 defined by the drying cylinder3a and the suction roll 4. Since the roll 4 is a suction roll, the paperweb 9 follows along with the drying wire 5 in the passage of this wirealong the curved path defined by the guiding rolls 6. Here, the paperweb 9 is urged against the drying wire by differential pressure createdby the hot air drying hood 7 above the curved path and the suctionchamber 8 within the curved path, and the drying air flows'through thepaper web 9 and drying wire 5. Since another suction roll 4 has beenplaced at the end of the curved path, the paper web 9 is transferred tothe second drying cylinder 3b. From this drying cylinder 3b the paperweb 9 continues to another curved drying means of the kind described(not shown in its entirety). The drawing also shows blowing devices 11aand 11b used to blow hot air into the hoods 7 to produce pressure whichis higher than atmospheric pressure. Suction means 12a and 12b are usedto produce a vacuum in the suction chambers 8, while suction means 126produce vacuum in the suction box 2. The walls of the hoods 7, suctionchambers 8 and suction box 2 are indicated by the numeral 14 in thedrawing, while sealing strips associated with these walls are indicatedby the numeral 13.

In the embodiment example of FIG. 2 the drying means are likewisearranged in two rows, one above the other, interspaced with each other.The drying wire 5 runs along a zigzag path over the,said drying means,from one row to the other. The drying means in the lower row areconventional heatable drying cylinders 3a, 3b, 3c, etc. The drying meansin the upper row are drying cylinders 10a, 10b, etc. permeable to air.As has been said above, the drying wire 5 travels together with thepaper web along a zigzag path from one row to the other. Similarly as inthe preceding embodiment, in this design, too, and for the same reasons,heavy-duty hot air blowing hoods 7 and suction chambers 8 have beenprovided. From the drawing it is understood that impingement drying iseffected in the region of the blowing hoods 7. For conduction of thepaper web 9 from the press section to the drying cylinder 3a, a suctionroll 1 and suction box 2 have been provided as in the precedingembodiment example. The paper web travels over the drying cylinders 3a,3b and 3c in the lower row, pressed against them by the drying wire 5.In its travel over the drying cylinders 10a and 10b, permeable to air,in the upper row, the paper web 9 is urged against the drying wire 5 byeffect of the hot air drying hood 7 and the suction chamber 8. Inaddition to blowing devices 11a and 11b, FIG. 2 also shows a blowingdevice applied to the third hood 7.

In both embodiment examples presented in the foregoing, the paper web isalternatingly subjected to contact drying and to perfusion drying. Thisresults in a faster drying of the paper web than in prior art.

The invention is by no means confined merely to the embodiment examplespresented here; these may rather be modified in many ways within thescope of the invention.

I claim:

1. In a paper machine, a dryer assembly for the drying of a paper web,comprising a row of drying cylinders rotatable about their horizontalaxes; perfusion drying means disposed at a vertical distance from therow of drying cylinders and located between said drying cylinders intheir interstices; a drying wire permeable to air, the paper webtraveling in contact with and supported by said wire from the beginningto the end of the dryer assembly all the way zigzagging from thepreceding drying cylinder to the next perfusion drying means, the paperweb being disposed on that side of the drying wire where, when runningupon a drying cylinder, the paper web is interposed between the dryingwire and the mantle surface of the drying cylinder so that hereby, thedrying of the paper web by contact drying takes place; said perfusiondrying means further comprising, on the side facing the drying wire andadjacent to it, a hot air blowing hood, and on the other side of thedrying wire and paper web opposite thereto, a suction chamber extendingand limited to the entire joint run of web and wire from one dryingcylinder to the next, so that perfusion drying of the paper web takesplace substantially on the whole distance of travel ofthe paper web fromthe preceding to the next drying cylinder, and so that dryingfurthermore takes place by impingement drying in the region of theblowing hood; a suction roll at the beginning of the dryer assembly andat a vertical distance from the first drying cylinder so that, by meansof said suction roll, the paper web is transferred to be supported bythe drying wire; a joint run of the paper web and drying wire betweensaid suction roll and first drying cylinder; a suction box on said jointrun on the side facing the drying wire, the effect of the vacuum in thissuction box being used to make the paper web adhere to the drying wire.

2. Dryer assembly according to claim 1, wherein the perfusion dryingmeans comprise a plurality of guiding rolls, the axes of which lie on acurved surface between mutually adjacent drying cylinders, and whereby,under guidance of said guiding rolls, the drying wire travels from onerow of drying cylinders to the next row, the perfusion drying meansfurther comprising, adjacent to the outermost guiding rolls, a wallwhich, together with the drying wire guided by the guiding rolls,confines and encloses said suction chamber.

3. Dryer assembly according to claim 2, wherein the outermost guidingrolls are suction rolls and are so placed to define a press nip togetherwith the drying cylinders adjacent to them.

4. Dryer assembly according to claim 1, wherein the perfusion dryingmeans comprises a row of cylinders permeable to air and rotatable abouttheir horizontal axes, said row being disposed at a vertical distancefrom the row of drying cylinders and said hot air blowing hood coveringsaid permeable-to-air cylinders on a sector of substantially and aconfining wall located adjacent to the plane defined by the row ofdrying cylinders and which, together with the runs of the drying wirebetween the drying cylinders and the cylinder permeable to air, confineand enclose said suction chamber.

1. In a paper machine, a dryer assembly for the drying of a paper web, comprising a row of drying cylinders rotatable about their horizontal axes; perfusion drying means disposed at a vertical distance from the row of drying cylinders and located between said drying cylinders in their interstices; a drying wire permeable to air, the paper web traveling in contact with and supported by said wire from the beginning to the end of the dryer assembly all the way zigzagging from the preceding drying cylinder to the next perfusion drying means, the paper web being disposed on that side of the drying wire where, when running upon a drying cylinder, the paper web is interposed between the drying wire and the mantle surface of the drying cylinder so that hereby, the drying of the paper web by contact drying takes place; said perfusion drying means further comprising, on the side facing the drying wire and adjacent to it, a hot air blowing hood, and on the other side of the drying wire and paper web opposite thereto, a suction chamber extending and limited to the entire joint run of web and wire from one drying cylinder to the next, so that perfusion drying of the paper web takes place substantially on the whole distance of travel of the paper web from the preceding to the next drying cylinder, and so that drying furthermore takes place by impingement drying in the region of the blowing hood; a suction roll at the beginning of the dryer assembly and at a vertical distance from the first drying cylinder so that, by means of said suction roll, the paper web is transferred to be supported by the drying wire; a joint run of the paper web and drying wire between said suction roll and first drying cylinder; a suction box on said joint run on the side facing the drying wire, the effect of the vacuum in this suction box being used to make the paper web adhere to the drying wire.
 2. Dryer assembly according to claim 1, wherein the perfusion drying means comprise a plurality of guiding rolls, the axes of which lie on a curved surface between mutually adjacent drying cylinders, and whereby, under guidance of said guiding rolls, the drying wire travels from one row of drying cylinders to the next row, the perfusion drying means further comprising, adjacent to the outermost guiding rolls, a wall which, together with the drying wire guided by the guiding rolls, confines and encloses said suction chamber.
 3. Dryer assembly according to claim 2, wherein the outermost guiding rolls are suction rolls and are so placed to define a press nip together with the drying cylinders adjacent to them.
 4. Dryer assembly according to claim 1, wherein the perfusion drying means comprises a row of cylinders permeable to air and rotatable about their horizontal axes, said Row being disposed at a vertical distance from the row of drying cylinders and said hot air blowing hood covering said permeable-to-air cylinders on a sector of substantially 180*, and a confining wall located adjacent to the plane defined by the row of drying cylinders and which, together with the runs of the drying wire between the drying cylinders and the cylinder permeable to air, confine and enclose said suction chamber. 